[ANGLÈS] Phenolic compounds are one of the main causes of environmental pollution of soils and water for their toxicity and persistence. Currently, phenolic compounds detection is principally done with bulky and expensive equipment (e.g. HPLC) in the laboratory environment. This detection requires sample transport and sometimes pre-treatment which makes this determination long and expensive. An integrated, low-cost, portable and robust system for quick in situ determination of phenolic compounds would be, therefore, very desirable. According to this, the objective of this work is to develop a biophotonic lab-on-a-chip with an organic matrix of alginate incorporating genetically modified E.coli trapped inside to determine the presence of phenolic compounds, and particularly catechol, in water samples. The alginate hydrogel will be used as a light guide, confining the light inside of it. For this reason, physico-chemical properties of alginate hydrogels (e.g. optical, diffusional, structural, etc.) containing different alginate concentrations with and without bacteria were evaluated and optimized. Finally, the alginate light guide containing bacteria was used for catechol determination in water samples. This architecture should open the possibility for in situ determination of phenolic compounds.